Field of Endeavor
The present application relates to additive manufacturing and more particularly to stereolithography additive manufacturing.
State of Technology
This section provides background information related to the present disclosure which is not necessarily prior art.
Additive manufacturing (AM) systems allow direct translation of software models into physical objects. AM systems follow a basic principle: generate three-dimensional structures from sequential two-dimensional patterns. Many different methods exist, such as laser sintering metals, photo-patterning polymers, or photo curing printed resins. Originally used for rapid prototyping, AM systems are increasingly used to fabricate operational components, particularly when desired geometry is too complicated for traditional machining approaches or only a low number of units are required.
Projection stereolithography is a polymer AM technology that uses dynamic photo masks to sequentially project two-dimensional cross sections of a three-dimensional structure into a photo curable resin. The desired structure is first generated using desktop computer aided design (CAD) software or other computational means and converted to a model file format. The model file is then processed by the system control software, which generates a series of two-dimensional cross sectional images at periodic intervals along the structure. The controller then projects these images with an ultraviolet projector onto a photosensitive resin, solidifying the pattern. After the layer is fully cured, the structure is lowered by a mechanical stage into the resin, allowing the resin to cover the top of the structure so the next layer can be patterned.
Polymer-based AM techniques are increasingly used to fabricate custom-made soft devices and biological research platforms. The high-resolution capability of SL systems and use of compliant polymers allows for the creation of highly specific devices, such as custom-fit ear buds. In biological research, three-dimensional hydrogel constructs provide an environment that closely mimics the native environment of cells, making it an attractive platform for studying cell interactions. For tissue engineering applications, AM systems can create scaffolds in the shape of missing structures, such as noses or ears. In many of these instances, the resin is highly specialized and not readily available, either due to low available supply (i.e. from patients) or high cost, so minimizing wasted resin is a priority.
The method for handling resin is central to improving process throughput and reducing material waste. Projection stereolithography systems project a photopattern onto a bath of resin covered by an ultraviolet transparent membrane. This membrane also serves a dual purpose of allowing oxygen to pass, inhibiting polymerization in a thin film at the interface with the resin to prevent adhesion between the cured layer and the membrane. Nonetheless, a certain suction force still exists when the part is pulled away from the membrane between layers, potentially deforming the part, delaminating the last layer, or detaching the whole part from the moving stage. In the case of high-speed printing, this suction force can become disruptive to membrane alignment and part stability.
The projection stereolithography approach is both high-resolution and high-speed, with speed limited only by resin cure time and movement of the mechanical stages. It is desirable for improved fabrication speed to efficiently manipulate the resin to minimize the translation required of the stage. Furthermore, projection stereolithography systems are usually constrained to a single material type, limiting potential applications. Improving the resin handling system will allow for multiple materials during fabrication, opening up new possibilities in tissue engineering and mechanical applications.
Present SL solutions provide a high-resolution method of patterning polymer structures. However, the resin-handling systems do not allow flexibility in material selection or composition, limit fabrication speed, and require large volumes. A system that addresses these shortcomings would expand the capabilities of existing projection stereolithography technology and enable new applications.